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A145713 Number of primes p in the range 9 < p <= prime(10^n) that begin and end with the same digit. 4

%I

%S 1,10,105,1180,14143,158036,1703161,17520558,157563619,1431557207

%N Number of primes p in the range 9 < p <= prime(10^n) that begin and end with the same digit.

%F a(n) = A145709(n) + A145710(n) + A145711(n) + A145712(n). [R. J. Mathar, Aug 02 2010]

%e The initial 1 is from the prime 11.

%e a(4)=1180 because to 10^4 or 10000 primes, ending in 104729=A006988(4), there are 1180 primes with equal and distinct first and last digits: 1 and 1, 3 and 3, 7 and 7 and 9 and 9.

%Y Cf. A145709 - A145712

%K hard,more,nonn,base

%O 1,2

%A _Enoch Haga_, Oct 16 2008

%E Edited by _N. J. A. Sloane_, Aug 16 2010

%E a(6) corrected and a(7)-a(10) added by _D. S. McNeil_, Aug 29 2010

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Last modified February 5 10:17 EST 2023. Contains 360084 sequences. (Running on oeis4.)